<fluent-accordion-item id="xxx"
                       expanded
                       unknown1="unknown1s-value"
                       unknown2="unknown2s-value"
                       blazor:elementReference="4260292c-daae-4cae-b314-81177813e8b0">
    <span slot="heading">
        custom
        heading value
    </span>
    child content
</fluent-accordion-item>